Touch screens and touch screen systems in general are well known in the technology of today. They are frequently used in a vast variety of applications, including for example automated teller machines (ATM) and industrial processing machines. Touch screens and touch screen systems are in particular used to replace or supplement conventional input systems such as the keyboard and/or mouse of a computer or similar.
A touch on a touch screen in an ordinary touch screen system causes the system to calculate the X and Y coordinates of the touch. The coordinates are typically calculated by a personal computer (PC) or some other suitable control unit connected to the touch screen.
The touch screen of an ordinary touch screen system is typically arranged on the surface of a display unit, e.g. on the surface of a CRT screen, a plasma screen or a LCD screen, or on the surface of some other suitable screen or similar that can be used for displaying images and/or other information.
In applications where the touch screen is arranged on the surface of a display unit it is common to connect both the touch screen and the display unit to the same computer or control unit, or alternatively to connect the computer(s) and/or the control unit(s) to each other in case the touch screen and the display unit is connected to separate computers or units. This will enable the computer or control unit to correlate the X and Y coordinates of the touch with an image displayed on the display unit so as to detect and recognise the touch of a certain object in the displayed image. This is a common and well known touch system technique that needs no further explanation.
A variety of well known touch-sensing technologies are commonly applied in connection with touch screen systems, including e.g. acoustic, resistive, capacitive and infrared technologies. These technologies are traditionally implemented to detect a sequence of touches that occur one at the time, i.e. they are in many cases unable to distinguish one touch from another, especially if the touches occur simultaneously.
However, improvements have been made, which enable a detection and resolving of several overlapping touches, e.g. by means of sampling techniques utilizing the fact that two touches are rarely occurring exactly simultaneously and/or the fact that two touches are usually made by different forces and/or occupies smaller or larger areas of the touch screen, see e.g. the U.S. Pat. No. 6,856,259.
However, even if several touches occurring substantially simultaneously can be distinguished from each other to some extent, known touch screen technologies cannot distinguish a touch made by a first user from a touch made by a second user, i.e. known touch screen systems treat all touches as originating from a single user, or alternatively from an unknown user.
This is a clear disadvantage in applications where a touch screen or a touch screen system is simultaneously used by a plurality of users, which may be the case e.g. in game play and gambling applications, or in connection with collaboration in office environments, or in collaboration in a command centre, e.g. for military operations or disaster relief etc.
Consequently, there is a need for an improved touch screen and touch screen system that enables a touch on the touch sensitive screen to be associated with a certain user of the touch screen and the touch screen system.